This invention relates to a mounting arrangement for light emitting devices, and in particular for semiconductor light emitting diodes.
Semiconductor light emitting diodes have recently found extensive use as replacements for filament bulbs in a wide variety of applications. Their small size, low power consumption and long life makes them attractive for such uses as indicator lamps in key telephone sets and switchboards. Careful consideration must be given in such uses for distributing the light to produce maximum impact on the viewer. In this regard, the small size of the diode (approx. 15 mils on each side) is a drawback since light is emitted from too small an area for good viewing. In order to overcome this problem, it is necessary to spread the light over a larger area while maintaining sufficient brightness. This may be accomplished for example by use of parabolic reflectors (see, e.g., U.S. Pat. No. 3,512,027 issued to Kupsky) or various lens arrangements for providing a diffuse image of the light (see, e.g., U.S. Pat. No. 3,780,358 issued to Haitz). In one approach, a faceted reflector is used to create several images of the diode (see U.S. Pat. No. 3,555,335 issued to B. H. Johnson). Another problem associated with the use of semiconductor diodes as indicator lamps is to provide enough contrast so that when the light is on it will be visible against its background, and when it is off reflected light from the ambient will not make it appear that it is on. To overcome this effect contrast filters are usually provided.
A further problem which should be overcome is the provision for good off-axis viewing. That is, the light should be visible over a wide angular range in order to be viewable from different areas of a room.
It is therefore a primary object of the invention to provide a mounting arrangement for semiconductor light emitting devices which produces a maximum impact of the emitted light on the viewer.